Method of die casting



April 29 1924. I 1

' C. PACK METHOD OFDIE' CASTING Filed Nov. 15 1922 4 2 sne ts sneet 1 Patented Apr. 29, 1924.

UNITED STATES PATENT OFFICE.

CHARLES PACK, OF ELMHURST, NEW YORK, ASSIGNOR TO DOEHLER DIE-CASTING COMPANY, A. CORPORATION OF NEW YORK.

METHOD OF DIE CASTING.

Application filed November 15, 1922. Serial No. 601,076.

To all whom it may concem:

Be it known that I, CHARLES PACK, a jcitizen of the United States, residing at .Elmhurst, in the county of Queens and State of New York, have invented certain new and useful Improvements in Methods of Die Casting, of which the fOllOWing is a full, clear, and exact description.

My invention relates to the art of diecasting and has particular reference to the coring of castings having one or more undercuts which prevent the withdrawal of the core. Where the undercutting is the result of the presence of a delicate or intricate design on the cored surface, the molding surface of the core must be of a sufficiently high melting point to retain its pattern accurately when the casting is poured; in other words the core must have a melting point at least substantially as high as that of the metal of the casting. This fact precludes the possibility of using a fusible core in such a case.

While this problem is frequently encountered in the practice of die-casting, a good example of its presentation is in the casting of molds for golf balls, and for that reason I have selected the casting of such molds for the explanation of my invention, it being understood, however, that my method is of general application wherever the nature of the casting requires it.

As is well known, the surface of substantially all golf ballsis characterized by a design formed of dimples or small depressions symmetrically and closely arranged. One of the last operations in the formation of the balls is the molding of this design in the surface, the mold consisting of two hemispherically recessed mold parts the molding surface of which has small rounded elevations complementary to the dimples. in the surface of the ball. Heretofore these molds have been nachined out at comparatively large expense, but my method provides a Way to die-cast them, thereby very materially reducing their cost.

In accordance with my invention, I first make the core of the necessary size, shape and surface configuration, and with a proper die make the cast about the core.

The casting with the core locked therein is then removed from the die and the inside of the core is removed in any suitable way leaving only a thin and easily distortable shell in the cavity, which can easily be withdrawn from the casting. This inside of the core may be removed by drilling or boring it out if the core is integral throughout, or if preferred the core may be made with the shell separately formed and fitting over an internal filler or auxiliary core which is removable after the casting is formed.

To facilitate the distortion of the shell so as to reduce its cross sectional dimension the requisite amount, I so proportion the die and core that the face of the casting about the exposed end of the core may be machined off, leaving the core protruding somewhat, and a tool is then easily applied to this protruding rim after the core has been reduced to a thin shell.

My invention also comprehends otherfeatures as will appear from the following description. I shall now describe my method with the aid of the accompanying drawings in which I show apparatus suitable for one adaptation of my invention, and shall thereafter point out my invention in claims.

Fig. 1 is an elevation of a core for use in die-casting a golf ball mold.

Fig. 2 is a cross section of the same on line 22 of Figure 1.

Fig. 3 is a section of an assembled die with the core in place.

Fig. 4 is an outside elevation of the half die carrying the core.

Fig. 5 is an elevation of the casting and core.

Fig. 6 isa section of the same after the casting has been machined. I

Fig. 7 is a section after the core has been reduced to a shell.

Fig. 8 is a view similar to Figure 7 showing the shell distorted and ready for withdrawal from the moldcavity.

While the core element shown in detailin Figures 1 and 2 may be formed in any suitable way, I prefer to turn it from bar stock for reasons which will hereinafter appear, and then machine the dimples in the molding surface. It may be composed of any metal suitable for the purpose, such as aluminum, aluminum alloys, brass, bronze, etc. I have found pure aluminum very satisfactory since it machines easily and yet has a sufficiently high melting point to enable it to retain its surface design at the temperature to which it is subjected during the casting operation. Thecore, as

the depressions or dimples 2, are formed in any suitable way, asby machining, the

diameter and surface configuration of the' portion 1 being a replica of one half of a. golf ball. This hemispherical end merges into a plain, cylindrical zone or band 3 of proper width, the forward limitation of which is indicated by the dotted diametral line in Figure 1. The purpose of this band will presently appear. Back of the zone 3 the diameter is reduced to form a shank or stem 4 for anchoring in the die.

The two halves of the die are shown in Figure 3, the one half 5 containing the mold cavity 6 and carrying the core, and the other half 7 contaming the gate or sprue opening 8. The mold cavity 6 is shown as undercut, being of substantially frusto-conical shape. Therefore, the mold 9, as shown in Figures 5 to 8, has its side walls thicker at the top than would be the case if the top diameter were the same as the bottom diameter. Due to the pressure to which these molds are subjected in the molding of golf balls, it is desirable to provide this substantial thickness of wall throughout.

To enable the removal of the mold 9 from 1 the die, the half 5 of the die is made in two parts, dividing on the central transverse line 5, as shown in Figures 3 and 4:.

Any suitable metal may be used for the casting, such as a copper alloy of aluminum.

' adhere to the core.

Following the casting operation, the core and casting are removed from the die, appearing at that point as shown in Figure 5. The round bosses or elevations 10 on the upper part of the surface of the concavity of the mold 9 interlock with the corresponding dimples in the core face so as to prevent the withdrawal of the core. The mold may now be "mounted for machining with respect to the shank or stem 4, and since the core was originally turned, it follows that the mold may be accurately machined about the axis of the core as a center. In this operation the face of the mold surroundin the core is machined down to the diametra line of the core, which is the dotted line indicated in Figure 1, thereby reducing the mold cavity to an exact hemisphere while leaving the zone 3 of the core protruding beyond the face of the mold. This condition is shown in Figure 6.

The next step is to cut 0E the stem 4 and to grind out or otherwise remove the interior of the core until only a thin shell is left. This stage is shown in Figure 7. lit is now a simple matter to apply a proper tool to the projecting lip 3 of the thin shell and contract the cross sectional dimension of the outer end of the shell sufliciently to release the projections 10 on the side wall of the mold cavity from the corresponding dimples 2 in the face of the core, as shown in Figure 8, and enable the core to be withdrawn.

It is obvious that my invention is in no wise confined to the particular details of the steps as explained above, but that the details may be variously modified'by .those skilled in the art to adapt the method to particular conditions without departing from the spirit and scope of my invention as pointed out in the appended claims.

I claim:-

1. The method of making die-castings having an internal undercut consisting of forming a core with a unitary molding surface portion, die-casting directly upon the molding surface of the core, removing the interior of the core leaving a relatively thin integral shell, and then distorting the thin shell to reduce its cross sectional dimension sufliciently to allow withdrawal of the shell from the casting. 2. Thef method of making die-castings having an internal undercut consisting in forming a solidmetal core with its molding surface including a portion complementary to the desired undercut, die-casting directly upon the molding surface of the core, removing the interior of the core leaving a relatively thin integral shell, and then distorting the thin shell to reduce its cross sectional dimension opposite the undercut sufiiciently to allow withdrawal of the shell from the casting.

3. The method of making die-castings having an internal undercut consisting 1n die-casting around a suitable core, removing the face of the casting surrounding the core sufliciently to expose the end of the core somewhat, reducing the core to a thin shell, and applying a contracting force to the protruding rim of the shell sufficiently to release the shell from the casting andpermit its withdrawal.

4. The method of making a die-casting having a concavity therein consisting in forming a suitable core having a supporting shank, die-casting about the core, supporting the casting from the shank of the core and machining the casting while so supported, and then separating the core and casting.

5. The .method of die-casting a mold for golf balls or the like consisting in forming a hemispherical metal core having the diameter and surface configuration of the ball to be molded, die-casting the mold directly upon the said core, removing the inside of the core leaving a thin hemispherical shell, and then contracting the diameter:

free tobe removed from the mold.

molded and continuing back from the mold- -6. The method of die-casting a mold for golf balls or the dike consisting in forming a core element provided on its end with a hemispherical molding surface having the configuration of one half of the ball to be ing surface into a substantially cylindrical extension, then die-casting themold directly upon the core, and then removing the portion of the casting surrounding the said cylindrical extension.

7. The method of die-casting a mold for golf balls or the like consisting in forming a core element provided on its end with a hemispherical molding surface having the configuration of one half of the ball to be molded and continuing back from the mold ing surface into a substantially cylindrical extension, then die-casting the mold directly upon the core, then removing the portion of the casting surrounding the said cylindrical extension, then removing the inside of the core leaving a thin shell, and then applying a contracting force to the protruding rim of the shell sufiicient to release the shell from the casting and permit its withdrawal.

8. The method of die-casting a mold for golf balls or the-like consisting in turn ing from relatively soft bar metal a' cylindrical core element having one end rounded to form a hemispherical molding surface with the configuration of one half of the ball to be molded and having its other end reduced to form an anchoring shank or stem, casting the mold directly upon the core, machining off the part of the casting surrounding the cylindrical portion of the core, cutting off the stem and drilling out the inside of the core leaving a thin shell,

and then applying a contracting force to the protruding rim of the shell sufficient to release theshell from the casting and permit its withdrawal. v

In witness whereof, I hereunto subscribe my signature.

CHARLES PACK. 

